This invention relates to a thermally developing apparatus and the thermally developing method, and in particular, to a thermally developing apparatus and the thermally developing method wherein image formation is carried out by holding a material to be developed by heat (hereinafter referred to as a thermally developable material) around the outer circumferential surface of a heated drum.
Thermally developing apparatus have been developed which is capable of forming a visible image from an image which has been formed as a latent image by continuously supplying a sheet-shaped thermally developable material to the outer circumferential surface of a heated drum to cause a thermal reaction to occur in this thermally developable material (refer to TOKUHYOHEI 10-500497 and TOKUHYOHEI 10-500506). According to these thermally developing apparatus, a sheet-shaped thermally developable material is supplied to the outer circumferential surface of a drum rotating at a constant rotational speed, and after the drum has rotated for a predetermined rotary angle with the thermally developable material being held, the thermally developable material is detached from the outer circumferential surface of the drum, while a new thermally developable material is simultaneously supplied to the circumferential surface of the drum; hence, it is possible to heat sheet-shaped thermally developable materials efficiently.
However, it has been proved that sometimes thermal development can not be enough made to reproduce the gradation suitably in a thermally developing apparatus, wherein a thermally developable material which comprises photosensitive silver halide particles, an organic silver salt, and a silver ion reducing agent, and is to be thermally developed at a temperature equal to or higher than the lowest development temperature, which should be higher equal to or higher than 80xc2x0 C., is thermally developed by heat generated by a heater.
In respect of this, for example, in the description of TOKUHYOHEI 10-500497 and TOKUHYOHEI 10-500506, the relationship between the maximum amount of heat generation that the heater in the thermal development section can generate while a sheet of thermally developable material is thermally developed and the heat capacity of the thermally developable material is not concretely described.
Further, a thermally developable material which comprises photosensitive silver halide particles, an organic silver salt, and a silver ion reducing agent, and is to be thermally developed at a temperature equal to or higher than the lowest development temperature, which should be equal to or higher than 80xc2x0 C., is easy to have a density unevenness owing to the non-uniformity of the temperature in the order of xc2x10.5xc2x0 C., which is different from the case of a usual thermally developable material.
It is an object of this invention to make it possible to make a stable gradation reproduction at a low cost and simply by carrying out thermal development stably.
The above object can be attained by the following structures.
(1-1) A thermally developing apparatus for thermally developing a thermally developable material by heating the thermally developable material to 80xc2x0 C. or more, comprises:
thermally developing means having a heater and for thermally developing the thermally developable material with heat generated by the heater; and
a controller to control heat generation by the heater;
wherein the thermally developing means thermally develops the thermally developable material such that an amount M of heat given to the thermally developable material during thermally developing a single sheet of the thermally developable material satisfies the following formula for a maximum amount Hmax of heat generation of the heater:
0.07xe2x89xa6M/Hmaxxe2x89xa60.75
(1-2) In the thermally developing apparatus of (1-1), the thermally developing apparatus further comprises:
cooling means for cooling the thermally developing means.
(1-3) In the thermally developing apparatus of (1-2), the cooling means forcedly cools the thermally developing means.
(1-4) In the thermally developing apparatus of (1-1), the thermally developing means comprises a heating member heated by the heater and the thermally developing apparatus comprises temperature detecting means for detecting the temperature of the heating member, and wherein the controller controls heat generation of the heater in accordance with a temperature detected by the temperature detecting means.
(1-5) In the thermally developing apparatus of (1-4), the controller sets a target temperature for the heater and changes a set value of the target temperature in accordance with a timing when the thermally developing means develops the thermally developable material.
(1-6) In the thermally developing apparatus of (1-5), a set value of the target temperature for at least one heater provided to a region where all of the thermally developable materials passes is set higher at a timing when the thermally developable material is thermally developed than at the other timing.
(1-7) In the thermally developing apparatus of (1-5), a set value of the target temperature during a period from a time that a leading edge of the thermally developable material firstly comes in contact with the heating member to a time that a trailing edge of the thermally developable material firstly comes in contact with the heating member and a set value of the target temperature during the other period are smoothed by ramp processing.
(1-8) The thermally developing apparatus of (1-4), the heating comprises a metallic supporting member having a heating surface and the heater is a plane-shaped heater provided so as to come in close contact with a surface of the supporting member at a side opposite to the side of the heating surface.
(1-9) In the thermally developing apparatus of (1-4), the controller controls the heater by using at least one of a value corresponding to a time integral value of the temperature detected by the temperature detecting means.
(1-10) In the thermally developing apparatus of (1-4), wherein the controller controls the heater by using a value corresponding to a time differential value of the temperature detected by the temperature detecting means.
(1-11) In the thermally developing apparatus of (1-4), the heater is operated ON-mode or OFF-mode and the controller controls the heater by a duty ratio of the ON-mode to the OFF-mode.
(1-12) In the thermally developing apparatus of (1-4), the thermally developing means comprises a thermally developing section to thermally develop the thermally developable material, the thermally developing section has an inner section covered with a heat insulating member and the heater and the heating member are provided in the inner section.
(1-13) In the thermally developing apparatus of (1-4), the heating member is a rotating member which heats the thermally developable material while rotating on a condition that the thermally developable material is in close contact with a outer circumferential surface of the rotating member.
(1-14) In the thermally developing apparatus of (1-13), the rotating member is divided in the axial direction into plural regions and each of the plural regions is provided with the heater.
(1-15) In the thermally developing apparatus of (1-4), the thermally developing apparatus further comprises:
supplying means for supplying the thermally developable material to the heating member, and
discharging means for discharging the thermally developable material from the heating member.
(1-16) In the thermally developing apparatus of (1-4), the heating member heats the thermally developable material with
a development temperature higher than a lowest development temperature for a development time.
(1-17) In the thermally developing apparatus of (1-1), the thermally developing apparatus further comprises:
a rotatable roller urged onto the heating member.
(1-18) In the thermally developing apparatus of (1-1), an elastic layer having a thickness of 0.1 mm or more is provided on the surface of the heating member.
(1-19) In the thermally developing apparatus of (1-18), a ratio of a thermal conductivity to the thickness of the elastic layer is 0.15 (W/m/xc2x0 K/mm) or more, and the heating member comprises a metallic supporting member to support directly or indirectly the elastic member.
(1-20) In the thermally developing apparatus of (1-19), the elastic layer has the thickness of 2 mm or less and the thermal conductivity of 0.3 W/m/xc2x0 K or more.
(1-21) A thermally developing apparatus for thermally developing a thermally developable material, comprises:
thermally developing means having a heater and for thermally developing the thermally developable material with heat generated by the heater; and
a controller to control heat generation by the heater;
wherein when the thermally developing means thermally develops a first thermally developable material having a largest width, the controller controls the heater such that an amount M1 of heat given to the first thermally developable material during thermally developing a single sheet of the first thermally developable material satisfies formula (1) for a maximum amount Hmax of heat generation of the heater during a developing time period for developing the first thermally developable material, and when the thermally developing means thermally develops a second thermally developable material having a smallest width, the controller controls the heater such that an amount M2 of heat given to the second thermally developable material during thermally developing a single sheet of the second thermally developable material satisfies formula (2) for a maximum amount Hmax of heat generation of the heater:
M1/Hmaxxe2x89xa60.75xe2x80x83xe2x80x83(1)
0.07xe2x89xa6M2/Hmaxxe2x80x83xe2x80x83(2)
(1-22) In the thermally developing apparatus of (1-21), the first thermally developable material has a heat capacity of a thermally developable material having the maximum heat capacity among thermally developable materials capable of being developed by the thermally developing apparatus and the second thermally developable material has a heat capacity of a thermally developable material having the minimum heat capacity among thermally developable materials capable of being developed by the thermally developing apparatus.
(1-23) In the thermally developing apparatus of (1-1) to (1-22), the thermally developing material is preferably a light sensitive material, especially a silver halide light sensitive material.
Further, the above object may be attained by the following preferable structures.
(2-1) The thermally developing apparatus of this invention is a thermally developing apparatus developing by heat (thermally developing) a thermally developable material which comprises photosensitive silver halide particles, an organic silver salt, and a silver ion reducing agent, and is to be thermally developed at a temperature equal to or higher than the lowest development temperature, which should be equal to or higher than 80xc2x0 C., by heat generated by a heater, wherein the maximum amount of heat generation Hmax that is to be generated by the heater in the thermal development section and an amount of heat M given to the thermally developable material during thermally developing a single sheet of the thermally while a sheet of thermally developable material is thermally developed satisfy the following formula:
0.07xe2x89xa6M/Hmaxxe2x89xa60.75.
According to the above-described relationship 0.07xe2x89xa6M/Hmax, it can be carried out a control to make a stable gradation reproduction at a low cost, with a duty ratio which is not made too small, and simply; further, according to the above-described relationship M/Hmaxxe2x89xa60.75, the temperature of the thermally developable material is stabilized, to carry out enough thermal development to make it possible to have a stable gradation reproduction owing to a sufficient margin of the heater, even if there is the variation of heat amount with the passage of time which is taken by the thermally developable material from the thermal development section.
Further, from the above-described point of view, it is desirable that 0.10xe2x89xa6M/Hmax (in particular, 0.15xe2x89xa6M/Hmax), and it is desirable that M/Hmaxxe2x89xa60.5 (in particular, M/Hmaxxe2x89xa60.3).
Further, because the lowest development temperature is equal to or higher than 80xc2x0 C., it is needless to say that thermal development can not substantially be made at a temperature equal to or lower than 40xc2x0 C.
(2-2) The thermally developing apparatus of this invention is a thermally developing apparatus thermally developing a thermally developable material which comprises photosensitive silver halide particles, an organic silver salt, and a silver ion reducing agent, and is to be thermally developed at a temperature equal to or higher than the lowest development temperature, which should be equal to or higher than 80xc2x0 C., by heat generated by a heater, said thermally developing apparatus further being capable of thermally developing thermally developable materials having different heat capacities respectively, wherein the maximum amount of heat generation Hmax that is to be generated by the heater in the thermal development section, an amount Mmax of heat given to the thermally developable material during thermally developing a single sheet of the thermally developable material having a largest width, and an amount Mmin of heat given to the thermally developable material during thermally developing a single sheet of the thermally developable material having a smallest width satisfy both of the following two inequalities:
Mmax/Hmaxxe2x89xa60.75, and
0.07xe2x89xa6Mmin/Hmax.
According to the above-described relationship 0.07xe2x89xa6Mmin/Hmax, it can be carried out a control to make a stable gradation reproduction at a low cost, with a duty ratio which is not made too small, and simply; further, according to the above-described relationship Mmax/Hmaxxe2x89xa60.75, the temperature of the thermally developable material is stabilized, to carry out enough thermal development to make it possible to have a stable gradation reproduction owing to a sufficient margin of the heater, even if there is the variation of heat quantity with the passage of time which is taken by the thermally developable material from the thermal development section.
Further, from the above-described point of view, it is desirable that 0.10 Mmin/Hmax (in particular, 0.12xe2x89xa6Mmin/Hmax), and it is desirable that Mmax/Hmaxxe2x89xa60.5 (in particular, Mmax/Hmaxxe2x89xa60.3).
(2-3) Further, by being equipped with a forced cooling means for compulsorily cooling the aforesaid thermally developable material, the thermally developing apparatus is capable of making a stable gradation reproduction owing to a temperature control being made easier against overheating.
(2-4) Further, it is desirable that, in the thermally developing apparatus comprising a heating member for heating the aforesaid thermally developable material being held by said heating member, temperature detecting means for detecting the temperature of said heating member, and temperature control means for controlling the aforesaid heater in accordance with the detected temperature, said heater is one for heating said heating member.
(2-5) Further, by making the target value of control for at least one of the portions of the aforesaid heater vary in accordance with the timing at which thermally developable materials are supplied, for example, by increasing the amount of heating by the heater while a thermally developable material is being supplied, and decreasing the amount of heating by the heater while no thermally developable material is being supplied, the temperature of the outer circumferential surface of the drum can be made uniform to the utmost, by which the unevenness of density can be suppressed.
(2-6) Further, regarding the target value of control for at least one of the portions of the heater provided in an area which all the thermally developable materials pass, if the value set in the time period substantially from the timing at which the leading edge of said thermally developable material first comes in contact with the aforesaid heating member to the timing at which the trailing edge of said thermally developable material first comes in contact with said heating member is made higher than the value set during the time period other than the above-described period, then the amount of heating by the heater is increased because the area which the thermally developable materials pass is cooled by them to produce a temperature drop while the thermally developable materials are being supplied, while the amount of heating by the heater is decreased while no thermally developable material is being supplied; thus, the temperature of the outer circumferential surface of the drum is made uniform to the utmost, by which the unevenness of density can be suppressed.
(2-7) It is desirable that, regarding the temperature control in which the value set in the time period substantially from the timing at which the leading edge of said thermally developable material first comes in contact with the aforesaid heating member to the timing at which the trailing edge of said thermally developable material first comes in contact with said heating member, and the value set during the time period other than the above-described period are made as target values, it is made smooth by ramp processing, by which a smoother temperature control becomes possible. In the above, the ramp processing means the processing which controls the temperature not to vary suddenly but gradually.
(2-8) Further, it is desirable that the aforesaid heating member comprises a supporting member made of a metal, and the aforesaid heater is a plane-shaped heater provided in contact with the opposite surface to the heating surface of said heating member; by using the above-described plane-shaped heater, it is possible to heat efficiently thermally developable materials which are supplied to said heating member, through said supporting member made of a metal having an excellent thermal conductivity.
(2-9) Further, it is desirable that the aforesaid temperature control means makes a temperature control using at least one of the value equivalent to the value integrated with time for the temperature detected by the aforesaid temperature detecting means, and the value equivalent to the value differentiated with time for the same; according to it, it is possible to make a control which converges the temperature rapidly to the target value.
(2-10) Further, it is desirable that the aforesaid temperature control means controls the aforesaid heater by a method of controlling the ON/OFF duty ratio, to make it possible to accomplish a control which has a simple structure and a good efficiency.
(2-11) Further, it is desirable that the aforesaid heating member and the aforesaid heater is provided in the thermal development section which is covered with a heat insulating member and heat-develops thermally developable materials by heating, because the heat dissipation from said heating member and said heater to the outside of said thermal development section can be suppressed, to make it possible to have a stable temperature control.
(2-12) Further, if the aforesaid heating member is a rotary member which carries out heating a thermally developable material held substantially in close contact with its outer circumferential surface while it is rotating, thermal development with a high efficiency can be accomplished, because thermally developable materials can be supplied continuously.
(2-13) Further, if the aforesaid portions of the heater are provided respectively in the plural areas formed by dividing the aforesaid rotary member in the direction of the axis of rotation, then the unevenness of density of the thermally developable materials can be suppressed regardless of the size, because the temperature of the aforesaid heating member can be adjusted in accordance with the thermally developable materials with a plurality of sizes having respectively different lengths in the direction of the axis of rotation of said rotary member.
(2-14) Further, it is desirable that the thermally developing apparatus further comprises supplying means for supplying a sheet-shaped thermally developable material to the aforesaid heating member, and ejecting means for ejecting a thermally developable material from said heating member.
(2-15) Further, if the aforesaid heating member is one that heats the aforesaid thermally developable material for a thermal development time at a development temperature which is equal to or higher than the aforesaid lowest development temperature, the generation of the unevenness of density can be suppressed, to obtain an image having a higher image quality.
(2-16) Further, if the thermally developing apparatus comprises rotatable rollers urged to the aforesaid heating member, by using these rollers, it is possible to make the aforesaid thermally developable material be in close contact with the outer circumferential surface of the drum.
(2-17) Further, if an elastic layer of a thickness equal to or larger than 0.1 mm is included in the surface portion of the aforesaid heating member, the condition of close contact between the thermally developable material and the heating member can be improved, to eliminate to the utmost portions of the thermally developable material which are not in contact with the heating member and are easy to have density unevenness.
(2-18) Further, if the ratio of the thermal conductivity to the thickness in the aforesaid elastic layer is equal to or larger than 0.15 (W/m/xc2x0 K/mm), and the aforesaid heating member includes a supporting member made of a metal supporting said elastic layer directly or indirectly, then the heat of the heating member can be easily transferred to the thermally developable material owing to the good thermal conductivity, and an image having a suitable density can be obtained.
(2-19) Further, if the aforesaid elastic layer has a thickness equal to or larger than 2mm and a thermal conductivity equal to or higher than 0.3 (W/m/xc2x0 K), then the unevenness of density can be suppressed, because the close contact condition and the thermal conductivity of the thermally developable material can be kept satisfactorily.
It is needless to say that the aforesaid xe2x80x9cwhile a sheet of a thermally developable material is thermally developedxe2x80x9d means xe2x80x9cfrom the timing at which the leading edge of a sheet of thermally developable material first comes in contact with the aforesaid heating member to the timing at which the trailing edge of said sheet of thermally developable material first comes in contact with said heating memberxe2x80x9d.
Further, it is needless to say that xe2x80x9cthe heat capacity M while a sheet of thermally developable material is thermally developedxe2x80x9d means xe2x80x9cthe heat quantity which is taken by a sheet of thermally developable material while the sheet of thermally developable material is thermally developedxe2x80x9d.
Further, it is needless to say that xe2x80x9cthe maximum amount of heat generation Hmax that is to be generated by the heater in the thermal development section while a sheet of thermally developable material is thermally developedxe2x80x9d means xe2x80x9cthe heat quantity generated under the condition that the heater in the thermal development section is let to generate heat at the maximum power during a time period equivalent to that while a sheet of thermally developable material is thermally developedxe2x80x9d. That is, the heat capacity M is an amount of heat which the developing means gives the thermally developable material.